This invention relates to illuminating means for color imaging sensing means for sensing the image of a diseased part or the like polychromatically by an endoscope assembly. Imaging sensing means have been employed using solid state image sensing elements for television cameras, endoscope assemblies, etc. Conventional endoscope assemblies employ so-called "image guide" and "light guide" comprising bundles of optical fibers, for example, several thousand of optical filaments, each having a diameter of several ten microns as image transferring means and light transferring means. In particular, in an endoscope assembly, a sensed image of an object to be observed is focussed at the tip of an image guide inserted from the operational trailing end to the vicinity of object by means of a focussing optical system (i.e. optical sensing system), transmitted to the trailing end and observed by means of an optical eyepiece system.
On the other hand, in an endoscope assembly employing said solid state image sensing element, it is preferable to display the image polychromatically in order to improve the visual diagnosis. Generally known means for providing color images include a combination of a color splitting optical system and three monochromatic solid state sensing means elements, or a combination of single solid-state image sensing element and a mosaic filter having a great number of red, green and blue color elements.
The former system has a disadvantage in that it is difficult to arrange a color splitting optical system and a plurality of solid-state image sensing elements in the thin and small space of an endoscope assembly. The latter system has also a disadvantage in that since light split into three colors is received, only 1/3 of the members in said solid-state image sensing element are allotted to each color, thereby reducing the resolving power when compared with that for a monochromatic image. Further, because the receiver elements for each color don't receive light at the same position, the colors are mixed insufficiently thus resulting in insufficient color matching.
For these reasons, in a prior art publication as disclosed in Published Japanese patent application No. 43686/1983, a plurality of light-reflecting means having selectivity of wave length such as dichroic mirrors are attached to the light source means at a suitable angles with regard to the illuminating optical system to provide light deflecting means for reflecting the illuminating light from the light source by means of said light-reflecting means to be guided to the light guide. Thus, the illumination successively of light of red, green and blue color is sensed by monochromatic solid state image sensing elements and stored in synchronized with the illumination in each frame memory or the like. These signals are read concurrently from these frame memories during regeneration to provide a color image.
In the above prior art, the arrangement of each dichroic mirror and optical deflector system, etc. is complicated and needs various adjustments and is therefore expensive and unsuitable for the mass production. The arrangement has low mechanical strength and said optical systems tend to be biased even by a small impact or the like such that a decrease in the illuminating light intensity and degradation in the color registration by the higher bias may result.
Moreover, in prior art as disclosed in Published Japanese patent application No. 90685/1978, three color filters are rotated by a motor to illuminate the three primary colors successively by a time division system. In this prior art, the filter should be rotated at a substantially high rate of rotation for regenerating one frame in 30 seconds as so images on conventional color televisions, which rate of revolution requires a relatively large motor. If the number of color filters attached to the supporter disk are increased, the rate of rotation may be reduced but the load is therefore increased excessively to cause the motor to overload.
As in the prior art when the filters are rotated by means of a motor, the motor is not incorporated in a small space. In addition, the motor issues noise having varied frequency causing an adverse effect on the vicinity. The mechanisms as illustrated by the above-mentioned prior art may be employed as illuminating means but not as image sensing means.